1. Field of the Invention
The present invention relates to a mechanical pencil in which a tubular shaft has at its front portion a slide member having a passage for a writing lead, and a lead advancement means axially slidably disposed in the tubular shaft.
2. Background Information
An example of the mechanical pencil of the type described which is shown in Japanese Pre-examined Utility Model Publication No. 56-44191 has a tubular shaft and an axially movable lead tank in the tubular shaft, and a chuck body is fixedly provided in front of the lead tank for the purpose of advancing the writing lead in the forward direction. At a front portion of the chuck body, a chuck ring is positioned around the chuck body to open/close the chuck body.
Further, a front member is fixed to the front end portion of the tubular shaft, and the front member has a passage for permitting the lead to move therethrough and, in addition, a slide member to which an anti-retraction member for the lead is press-fitted is arranged so that the slide member can project from an end of the front member.
In the known structure of the mechanical pencil described above, there is generally produced a gap or space between a rear end of a shortened residual lead (hereinafter referred to as a xe2x80x9cremaining leadxe2x80x9d) which has been positioned out of the chuck body and a front end of a succeeding (or, following) new lead (hereinafter referred to as a xe2x80x9csucceeding leadxe2x80x9d). This is caused by the following mechanism. Namely, the chuck body is closed by a chuck ring immediately before a retracting movement of the chuck body ends and is retracted grasping the succeeding lead. At this moment, however, the shortened remaining lead is positioned independent of the succeeding new lead and slightly held by the anti-retraction member in the front member so that the shortened lead is prevented from being retracted.
Once a gap as the gap described is produced, the remaining lead is retracted unexpectedly by a writing pressure in a writing operation and this results in a failure of writing and consequently a growth of feeling of wrongness.
Further, some users who dislike the above phenomena try to remove the remaining lead out of a lead guide member and operate to advance the next new lead. This will be a burden to an effective use of the shortened remaining leads.
In view of the above, it is an object of the present invention to provide a mechanical pencil which can abolish the disadvantages and difficulties appearing in the conventional structure described above and permits an effective use of the remaining leads.
According to a first aspect of the present invention, there is provided a mechanical pencil which comprises a tubular shaft having at its front portion a slide member having a passage for a writing lead, and a lead advancement means axially slidably disposed in the tubular shaft, wherein the slide member and at least one element of the lead advancement means are co-acted and interlocked with each other.
According to a second aspect of the invention, there is provided a mechanical pencil comprising a first chuck body at the rear portion of a second chuck body, the second chuck body grasping lead and releasing the same, the second chuck body having an anti-retraction member for softly holds the lead, wherein the first chuck body and the second chuck body are co-acted (interlocked) in the retraction movement thereof such that the retraction movement is conducted by a retraction of the first chuck body.
According to a third aspect of the invention, a slide member having a lead passage is disposed at a front portion of the tubular shaft, and a lead advancement (feeding) means is axially moveably disposed in the tubular shaft, wherein a knocking actuator member is provided to have a contact portion such that the contact portion is contacted with the slide member and the lead advancement (feed) member.
According to a fourth aspect of the invention, a slide member having a lead passage is disposed at a front portion of the tubular shaft and a lead advancement (feeding) means is axially moveably disposed in the tubular shaft, wherein the slide member is retracted by pushing a part of the tubular shaft.
In the structure of the mechanical pencil according to the invention, when the slider is retracted, a remaining (residual) lead is retracted with contacting with a succeeding lead.